late 14c., braggen "to make a loud sound," also "to talk boastfully," of obscure origin, perhaps related to bray of a trumpet and imitative, or related to the Middle English adjective brag "ostentatious, proud; spirited, brave" (early 14c.), which probably is from Celtic, and is the source of the surname Bragg ( ...

Where does the term bragging come from?

From Middle English braggen (“to make a loud noise; to speak boastfully”) of unknown origin. Possibly related to the Middle English adjective brag (“prideful; spirited”), which is probably of Celtic origin; or from Old Norse bragr (“best; foremost; poetry”); or through Old English from Old Norse braka (“to creak”).

When was the word brag invented?

The Oxford English Dictionary defines “brag” as “to vaunt, talk boastfully, boast oneself,” a usage first recorded in 1377.